Configurable thermoacoustic streaming by laser-induced temperature gradients

Area of Science:

• Acoustofluidics
• Microfluidics
• Biomedical Engineering

Background:

• Acoustically actuated microchannels enable precise control of micro-objects.
• Applications include rare cell studies and cell sorting.
• Acoustic body forces interact with fluid property gradients.

Purpose of the Study:

• To investigate the effect of optically induced temperature gradients on acoustic streaming flow.
• To demonstrate tunable control of microfluidic streaming using thermal fields.
• To analyze the transition of streaming patterns based on heat source location.

Main Methods:

• Inducing temperature gradients optically via light absorption in a microfluidic channel.
• Measuring streaming flow using 3D particle tracking.
• Conducting experiments and simulations under varying thermal conditions.

Main Results:

• Shifting heat source location changed streaming rolls from four to two.
• Modulating optical absorbance tuned streaming velocity; higher absorption increased speed.
• Asymmetric heat generation led to increased velocity components along the laser direction.

Conclusions:

• Optical control of thermal fields offers a method to manipulate acoustic streaming in microchannels.
• The study demonstrates a tunable platform for microfluidic manipulation.
• Findings have implications for targeted particle manipulation in biological and medical applications.